Regional Cover Characterisation of the Central Gawler – Clipping regolith-plant associations to better constrain geology and prospectivity

Petts, Anna1; Noble, Ryan2; and Reid, Nathan2

1Geological Survey of South Australia, Department for Energy and Mining, Adelaide, Australia; 2CSIRO, Mineral Resources, Discovery Program, Perth, Western Australia, Australia

Basement rocks and basin sediments seem far detached from surface features such as soils, landform features and plant assemblages. Regolith research in the last 50 years in Australia and abroad has proven many times that the types of assemblages of plants seen across a landscape is in fact well connected to the underlying geology, however, and therefore may be used to demarcate different regolith and landform features for mapping and for cover charactering. Also, these same plants will be linked to the geochemistry of the cover and underlying geological units through plant-nutrient cycling and groundwater uptake and therefore present a suitable, available and sometimes widespread sampling media for exploration geochemistry surveys and mining rehabilitation studies.

This concept has been tested in a regional survey across the Central Gawler Craton, of South Australia.  The Geological Survey of South Australia (GSSA) has collected 212 native plant samples as part of a wider collaboration with CSIRO Minerals. The biogeochemical analysis will be used in conjunction with over 150 CSIRO UltraFine+ (UF) soil results to constrain complex plant-soil chemical relationship as well as test exploration geochemistry applications for plants as regional sampling media. Biogeochemical surveys are becoming increasingly popular first-pass techniques for mineral exploration companies and the GSSA has identified the need to provide relevant regional datasets to assist with identification, analysis and interpretation of plant major and trace element levels. This will enable better confidence when using similar techniques as well as provide improved data reporting standards.

The the availability of select plant species (including Bladder Saltbush Atriplex vesicaria, Pearl bluebush Maireana sedifolia, Black bluebush Maireana pyramidata, Mulga Acacia aneura and Mallee) for sampling and mapping purposes has not been widely recorded analysed. Also the regolith-plant associations of the Central Gawler region, utilising current statewide and newly available regional regolith-landform map products, shows useful relationships and will contribute to accurate promotion of best biogeochemical practice in this region . The most widespread plant assemblage in the Central Gawler Craton UF survey area is chenopod shrubland, with the top two plant species sampled being Pearl Bluebush (47%) followed by Bladder Saltbush (39%) – based on data collected during fieldwork.


Biography

Anna has a keen interest in applying innovative exploration techniques for geochemistry and mineral exploration, as well as understanding fundamental regolith and landform processes. She completed her PhD in 2009 on using termite mounds as a sampling media, and has worked in exploration and mining as well as government.

About the GSA

The Geological Society of Australia was established as a non-profit organisation in 1952 to promote, advance and support Earth sciences in Australia.

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